An ecological study on childhood autism

St-Hilaire Sophie, Ezike, Stryhn Henrik, Thomas

Description

and methods Idiopathic autism, suspected to be caused by exposure of genetically susceptible individuals to unknown environmental triggers, has increased dramatically in the past 25 years. The objectives of our study were to determine, using a linear regression model, whether the county prevalence of autism in the Pacific Northwest of the United States was associated with the source of drinking water for that county and whether this relationship was dependent on the level of environmental pollutants and meteorological factors in the county. Results We found the previously reported relationship between precipitation and autism in a county was dependent on the amount of drinking water derived from surface sources in the county. We also found a positive association between the EPA’s risk of neurological disease and autism, but this relationship was only present in warm areas. Conclusions Our study provides evidence for the hypothesis that environmental factors are associated with autism and that meteorological factors play a role in this relationship.

Sujets

• Environmental factor
• Drinking water
• Air pollution
• Précipitation

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 14
• Langue: English

Extrait

StHilaireet al. International Journal of Health Geographics2012,11:44 http://www.ijhealthgeographics.com/content/11/1/44

INTERNATIONAL JOURNAL OF HEALTH GEOGRAPHICS

R E S E A R C HOpen Access An ecological study on childhood autism 1* 21 2 Sophie StHilaire ,Victor O Ezike , Henrik Stryhnand Michael A Thomas

Abstract Background and methods:Idiopathic autism, suspected to be caused by exposure of genetically susceptible individuals to unknown environmental triggers, has increased dramatically in the past 25 years. The objectives of our study were to determine, using a linear regression model, whether the county prevalence of autism in the Pacific Northwest of the United States was associated with the source of drinking water for that county and whether this relationship was dependent on the level of environmental pollutants and meteorological factors in the county. Results:We found the previously reported relationship between precipitation and autism in a county was dependent on the amount of drinking water derived from surface sources in the county. We also found a positive association between the EPA’s risk of neurological disease and autism, but this relationship was only present in warm areas. Conclusions:Our study provides evidence for the hypothesis that environmental factors are associated with autism and that meteorological factors play a role in this relationship. Keywords:Idiopathic autism, Environmental factors, Drinking water, Air pollutants, Precipitation

Background Autism spectrum disorders (ASDs) are a group of devel opmental disabilities characterized by impaired social skills and communication deficits, typically diagnosed by the age of three [13]. The incidence of ASDs has increased dramatically in the past 25 years, from 0.05% in the early 1980’s to 1.1% in 2008 [46]. The recent steady increase in ASDs, without a compensatory decrease in the diag nosis of other psychological conditions [7], is suggestive of an environmental disease caused by exposure to a risk factor(s) that is relatively widespread. Despite its increasing incidence, the causes of the majority of cases of ASDs remain unknown. One of the difficulties in investigating these diseases is the use of broad case definitions. Further, symptoms vary between patients; however, it is fairly well accepted that ASDs develop prenatally or within the first few years of life and, at least with high functioning autism, occur more frequently in males than females [5,8]. Several researchers have hypothesized about the possible role of serotonin and gammaaminobutyric acid

* Correspondence: [e-mail] 1 Department of Health Management, Atlantic Veterinary College, University of Prince Edward Island, 550 University Avenue, Charlottetown PE C1A 4P3, Canada Full list of author information is available at the end of the article

(GABA) in autism. WhitakerAzmitia [9] suggests that early exposure to high levels of serotonin while the brain is developing results in a negative feedback on the devel opment of serotonin terminals, and studies have demon strated this phenomenon in laboratory rats[10,11]. The reduction of serotonin terminals may then have cascad ing effects on a number of neurological pathways that are regulated by this neurotransmitter [12]. Other research ers have observed a dysfunction in the GABAergic sys tem of autistic individuals [13]. In laboratory studies on neonatal rats, exposure to high levels of extracellular GABAinduced neuronal cell death which persisted over time [14]. Exposure to compounds that could result in hyper serotonemia or other imbalances in neurotransmitters in pregnant women or in infants less than 2 years of age, when the blood brain barrier is still permeable [9], could occur via a number of ways, including inhalation of chemicals, consumption of contaminated food and water, and exposure to prescription or other drugs. Fetal exposure to cocaine, which results in hyperserotonemia, has been associated with an increased risk of autism [15]. The administration of selective serotonin reuptake inhibitors (SSRIs), or serotonin–norepinephrine reuptake inhibitors, in pregnant women is still practiced [16] and could result in higher than expected levels of serotonin in the fetus.

© 2012 StHilaire et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.